There is a established need in industry for a method of cooling workers in hot environments and treating heat stress. A pressing example is the recent notice of the increase in heart attack deaths of on duty firefighters. In fact of the 34 fireground deaths of 1993 over 52% of them were reported to be from heat stressed induced heart attacks. This is attributed to the mandated use of NFPA 500 clothing or bunker gear worn by fire fighters. (Physiological Responses to Working In Bunker Gear: A Comparative Study, Fire Engineering 11/94)The bunker gear has reduced bum deaths to less than 5% but the hot microclimate inside has added to the cardiovascular work load. Clearly this heat stress/overexertion induced heart attacks needs to be addressed and in a way that does not greatly increase the weight and hence work load of the fire fighter Most personal cooling devices cool the skin exclusively through conduction or evaporation with no regard for other methods. They are necessarily heavy and bulky and restrictive. The present invention uses an different method.
Cooling the chest even dramatically becomes ineffective in ambient environmental temperatures above 120.degree. F. due to the de-coupling between the blood flow and the skin on the torso. Cooling the skin causes the small blood vessels to constrict and reduce flow. Consequently only limited cooling of the body can occur by removing heat through the skin of ones torso and therefore a full body suit becomes necessary. However by cooling the breathing air, this decoupling does not as readily occur and hence the breathing air can be cooled far greater than could be tolerated on the torso or the head.